Fuel for vehicles has been produced in the past from the refining of crude oil. The refining process results in gasoline, jet fuel and diesel fuel. This source has been the mainstay of fuel for our transportation systems since the 1800s.
In 1955, synthetic oil was first produced from coal by Sasol, a South African group of companies in their Sasolburg plant, where it continues today. In the early 1950s Sasol pioneered the use of Fischer-Tropsch (F-T) catalysts, which converted the coal into fuels and chemicals. In particular, the Fischer-Tropsch process produces synthetic diesel fuel. To achieve the conversion, Sasol began to gasify the coal, a technology which is used today to produce synthesis gas, a mixture of predominantly carbon monoxide and hydrogen. The synthesis gas, as produced by via the Fischer-Tropsch process continues to be utilized for diesel fuel throughout the world, or as a feedstock for methanol production in areas which do not have a natural gas supply.
Over the years, variations on the process pioneered by Sasol have arisen from the original Fischer-Tropsch catalysts. Their major limitation is that they do not produce gasoline mixtures, only predominantly diesel-range mixtures, those being mostly paraffinic and aromatic hydrocarbons with a C10 to C15 carbon skeleton. Much research and effort has been undertaken to modify the original Fischer-Tropsch process to produce the gasoline-range mixtures, those having a C5 to C12 carbon skeleton, but to no avail.
More recently, under pressure from the global oil crisis, there has been concerted effort in the U.S. to develop chemical pathways to produce gasoline that do not involve Fischer-Tropsch catalysts. Modified methanol-production catalysts have been attempted, and the most promising routes involve the conversion of methanol into gasoline-range products. This work is largely theoretical and conducted by the large government-funded laboratories and universities.
A process to efficiently convert synthesis gas from any carbon-derived source to gasoline is urgently needed to solve the reduction in crude oil availability. The most rational route to gasoline is through conversion of organic, non-fossil, material such as biomass into synthesis gas. It is desirable to develop a process which allows for the energetically efficient conversion of synthesis gas into non-oxygenated hydrocarbons having a C5 to C12 carbon skeleton, for example, gasoline.
Researchers have investigated the conversion of synthesis gas into gasoline using specialized bacteria. However, this route is not as desirable as a chemical synthesis route because the bacterial culturing, care and feeding of the converting bacteria is more art than science. The process is similar to the production of ethanol through yeast, in that the bacteria must be kept in special heated vats, supplied with specific types and concentrations of synthesis gas and the resultant products must be continuously removed. As a further disadvantage to this route of gasoline synthesis, there are large thermal inefficiencies owing to the large amount of water which must be externally heated as required to complete the process and maintain the bacteria.
Therefore, it is highly desirable to develop a chemical route to gasoline carbon-range products which uses more energetically efficient routes of synthesis and one in which there is an abundance of inexpensive starting material. In order to make the process as efficient as possible, it is desirable to develop and utilize appropriate catalysts to maintain the number of process steps as low as possible, recycle by-products and un-reacted compounds from the various steps in the process back into the reactors to be re-reacted, and on which enables the production of relatively pure products in each reactor to be used in the process such that the next reactor in the process can run as efficiently as possible.